The field of the invention relates to electronically controlled throttle units in vehicles having a drive unit.
In some engines, an electronically controlled throttle is used for improved performance. In such systems, position of the throttle is controlled via closed loop feedback control. Typically, to provide redundancy multiple throttle position sensors are provided.
One method to provide two throttle position sensors uses sensors of different gradients, each linear over the entire operating range, another uses gradients of opposite sign. Still other methods use saturating sensors. These methods are described U.S. Pat. No. 5,136,880, U.S. Pat. No. 5,260,877, and U.S. Pat. No. 4,693,111, respectively.
The inventors herein have recognized some disadvantages of the above approaches. In particular, when a high resolution saturating sensor and a low resolution sensor are used together, there is a saturated region where the saturating sensor provides less information than the unsaturated region. Alternatively, when different gradients are used, each linear over the entire region, the analog to digital converters are over-specified and under-utilized to accommodate the low resolution sensor. Another disadvantage with prior approaches is that multiple tracks, interconnections between the tracks, and wiper arms may be required to provide multiple outputs having different characteristics.
An object of the present invention is to provide electronic throttle control systems and sensors.
The above object is achieved and disadvantages of prior approaches overcome by a position sensor according to the present invention. In one aspect, the sensor comprises a substrate, and a track positioned on said substrate including at least two contiguous first and second segments, each of said segments having a different material property.
By having a sensor with two operating regions, it is possible to obtain high resolution at low throttle angles, and thereby have better airflow control as well as to obtain information throughout the operating range without over-specifying and under-utilizing A/D converters.
An advantage of the above aspect of the invention is improved monitoring.
Another advantage of the above aspect of the invention is improved control.
In another aspect of the present invention, the sensor further comprises a single movable wiper for sliding over said track to provide an electrical signal having an amplitude related to position of said wiper.
An advantage of the above aspect of the present invention is that a simplified structure is provided with a single track having two segments, no interconnection between the segments, and only a single wiper arm moving across both segments.